CONTRAST for WSFACTORS (MANOVA: Repeated Measures command)

The levels of a within-subjects factor are represented by different dependent variables. Therefore, contrasts between levels of such a factor compare these dependent variables. Specifying the type of contrast amounts to specifying a transformation to be performed on the dependent variables.

  • An orthonormal transformation is automatically performed on the dependent variables in a repeated measures analysis.
  • To specify the type of orthonormal transformation, use the CONTRAST subcommand for the within-subjects factors.
  • Regardless of the contrast type you specify, the transformation matrix is orthonormalized before use.
  • If you do not specify a contrast type for within-subjects factors, the default contrast type is orthogonal POLYNOMIAL. Intrinsically orthogonal contrast types are recommended for within-subjects factors if you wish to examine each degree-of-freedom test. Other orthogonal contrast types are DIFFERENCE and HELMERT. MULTIV and AVERF tests are identical, no matter what contrast was specified.
  • To perform non-orthogonal contrasts, you must use the TRANSFORM subcommand instead of CONTRAST. The TRANSFORM subcommand is discussed in TRANSFORM Subcommand (MANOVA: Multivariate command).
  • When you implicitly request a transformation of the dependent variables with CONTRAST for within-subjects factors, the same transformation is applied to any covariates in the analysis. The number of covariates must be an integer multiple of the number of dependent variables.
  • You can display the transpose of the transformation matrix generated by your within-subjects contrast using the keyword TRANSFORM on the PRINT subcommand.

Example

MANOVA SCORE1 SCORE2 SCORE3 BY GROUP(1,4)
  /WSFACTORS=ROUND(3)
  /CONTRAST(ROUND)=DIFFERENCE
  /CONTRAST(GROUP)=DEVIATION
  /PRINT=TRANSFORM PARAM(ESTIM).
  • This analysis has one between-subjects factor, GROUP, with levels 1, 2, 3, and 4, and one within-subjects factor, ROUND, with three levels that are represented by the three dependent variables.
  • The first CONTRAST subcommand specifies difference contrasts for ROUND, the within-subjects factor.
  • There is no WSDESIGN subcommand, so a default full factorial within-subjects design is assumed. This could also have been specified as WSDESIGN=ROUND, or simply WSDESIGN.
  • The second CONTRAST subcommand specifies deviation contrasts for GROUP, the between-subjects factor. This subcommand could have been omitted because deviation contrasts are the default.
  • PRINT requests the display of the transformation matrix generated by the within-subjects contrast and the parameter estimates for the model.
  • There is no DESIGN subcommand, so a default full factorial between-subjects design is assumed. This could also have been specified as DESIGN=GROUP, or simply DESIGN.